$\begin{array}{l} x=\left( \begin{array}{c} n \hfill \\ k \hfill \\\end{array} \right) = \frac{ n!}{(n-k)!\cdot k!}\\\\ \\ \left( \begin{array}{c} n \hfill \\ k \hfill \\\end{array} \right)\\ \textbf{Gegeben:} \\ x=\left( \begin{array}{c} 6 \hfill \\ 3 \hfill \\\end{array} \right) = \frac{ 6!}{(6-3)!\cdot 3!}\\\\x=\#x\\ \\ \textbf{Rechnung:} \\x=\left( \begin{array}{c} 6 \\ 3 \\\end{array} \right) = \frac{ 6!}{(6-3)!\cdot 3!}\\\\x=20\\\\ \end{array}$